Derivative Instruments and Hedging Activities - Schedule of Notional Amounts of Outstanding Derivative Positions (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Foreign Exchange Contract
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 1,451	$ 2,735
Currency Swap | Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	1,958	1,958
Fixed to Floating | Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	700	700
Interest Rate Swap | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	1,000	1,000
Debt | Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 2,478	$ 2,543